Ecological services value of ‘natural-artificial’ water cycle: Valuation method and its application in the Yangtze River Basin of China

Abstract

This paper introduces an evaluation approach for the Ecological Service Value of Water (ESV-W) by coupling the assessment of Ecosystem Services Value (ESV) with the Water Allocation and Simulation Model (WAS). The proposed method is applied to evaluate ESV and ESV-W in the Yangtze River Basin from 2005 to 2020. Firstly, an improved Equivalence Factor (EF) method is employed to estimate ESV by considering different land use types and service categories. Then, the enhanced WAS model is used to quantify and identify the role of the ‘natural-artificial’ soil water cycle in supporting the ecological service functions. Finally, by integrating the ESV evaluation system with the WAS model, the evaluation method for ESV-W is established. The results indicated that from 2005 to 2020, the total ESV increased from 4.0 to 5.6 trillion US Dollars, with forests being the primary contributor among land use types (about 52%), and regulating services are dominating among service categories (about 70%). The spatial distribution of the ESV showed a decreasing trend from southeast to northwest in the Yangtze River Basin, while the ESV-W exhibited high values concentrated along the main stream of the upper reaches of the Yangtze River and lower in the middle. The ESV-W of the ‘natural’ soil water cycle still dominates (over 96%), but the ESV-W of the ‘artificial’ soil water cycle has been rapidly increasing in recent years. In 2020, the ESV-W per unit water of precipitation, irrigation, and ecological water were 4.0 Dollars/m3, 0.7 Dollars/m3, and 32.4 Dollars/m3, respectively. This study aims to provide references for the protection of water ecosystems and the sustainable utilization of water resources. It also serves as a reference for improving the evaluation system of ESV.